Auditory and Vestibular Flashcards
What are the cilia on hair cells responsible for?
Stimulus-responsive cation entry, cell body releases glutamate onto efferent nerve endings, afferent nerves regulate the response
What is sound?
Repetitive variations in a medium, such as air
Vibration of the eardurm, the malleus, the incus and the stapes spreads to the _____ where it is converted into movement/vibration of ______. The vibration in the cochlea is captured by ____ _____. Then via ___________ physical vibration is converted to neural energy which is percieved in the auditory cortex.
Vibration of the eardurm, the malleus, the incus and the stapes spreads to the cochlea where it is converted into movement/vibration of fluids. The vibration in the cochlea is captured by hair cells. Then via transduction physical vibration is converted to neural energy which is percieved in the auditory cortex.
What are the three mechanisms for impedance matching?
1) Area ratio of the ear drum to the stapes footplate (20:1)
2) lever action of the ossicles
3) bucling of the ear drum
The cochlea consists of three ______ _____ cavities
The cochlea consists of three fluid filled cavities
what separates scala vestibuli from scala media?
reissner’s membrane
what separates scala media from scala tympani?
basilar membrane
what is the path of conduction through the cochlea?
organ of corti hair cells -> basilar membrane to tectorial membrane
Where is scala media closed off?
At the apex
What connects ar the helicotrema?
Scala tympani and scala vestibuli
perilymph in scala _______ and scala _______ is continuous
perilymph in scala tympani and scala vestibuli is continuous
Scala tympani meets ____ window
Scala vestibuli meets _____ window
Scala tympani meets oval window
Scala vestibuli meets round window
pressure at oval window results in what?
Complimentary motion at round window
The middle of the basilar membrane vibrates for ____ frequency sound as it is _____ stiff and more ____.
The middle of the basilar membrane vibrates for lower frequency sound as it is less stiff and more wide.
The _____ and __________ of the basilar membrane determines the distance a particular frequency travels
The width and flexibility of the basilar membrane determines the distance a particular frequency travels
Where are hair cells located?
Between basilar membrane and reticular lamina, tips in the tectorial membrane
what are the two types of hair cell and what separates them?
inner (3500)
outer (15,000- 20,000)
separated by rods of corti
where do hair cells synapse?
on bipolar neurons with cell body in spiral ganglion
Describe hair cell transduction
The tectorial membrane vibrates and the hair cells (cilia) bend.
Depending on how they bend the hair cells release neurotransmitter.
The neurotransmitter released in the hair cell are captured in nerve fibres.
The hair cell K current is _______
The hair cell K current is inwards
Endolymph potential is __mV so generating a ___mV gradient across the stereocilia membrane
Endolymph potential is 80mV so generating a 120mV gradient across the stereocilia membrane
_____ hair cells are the main source of afferent signal in auditory nerve (__ afferents per hair cell). multiple outer hair cells are innervated by a ______ afferent.
Inner hair cells are the main source of afferent signal in auditory nerve (10 afferents per hair cell). multiple outer hair cells are innervated by a single afferent.
Outer hair cells primarily get _______ inputs, controls _________ and ______ membrane vibration.
Outer hair cells primarily get efferent inputs, controls stiffness and amplify membrane vibration.
Outer hair cells are often called the …..
Cochlear amplifier
Which protein can change the length of the cell?
Motor protein composed of prestin- changes the relationship between basilar membrane and tectorial membrane
Outer hair cells respond to sound with both a ________ _________ and a change in ______
Outer hair cells respond to sound with both a receptor potential and a change in length
How does furosemide affect outer hair cells?
Inactivates the membrane motor
Length change of OHC –> increased movement of ______ ______ –> increased bending of _____ ____ ____ -> transduction
Length change of OHC –> increased movement of basilar membrane –> increased bending of inner hair cells -> transduction
What are the two mechanisms for frequency coding?
Place code
Temporal code
Describe the central pathway of the auditory system?
Cochlea -> cochlear nucleus -> superior olive ( in pons) -> inferior colliculus (in midbrain) -> medial geniculate body (midbrain) -> auditory cortex
Where does the signal from one cochlea cross?
From cochlear nucleus to contalateral superior olive
What are the three cochlear nuclei?
Dorsal cochlear nucleus
Posteroventral cochlear nucleus
Anteroventral cochlear nucleus
Tonotopy (through _________ order) ensures that each neuron innervates several different areas and different neuron types
Tonotopy (through innervation order) ensures that each neuron innervates several different areas and different neuron types
What does the medial superior olive computing time at both ears allow?
Interaural time difference
From what does the lateral superior olive get an excitatory input?
From the ipsilateral anteroventral cochlear nucleus
the contralateral anteroventral cochlear nucleus input excites a neurone in the _____ __ ____ which sends an ________ signal to the lateral superior olive neurone
the contralateral anteroventral cochlear nucleus input excites a neurone in the calyx of held which sends an inhibitory signal to the lateral superior olive neurone
What is the calyx of held?
Medial nucleus of the Trapezoid Body
If the aural signal is closer to the ipsilateral ear, that lateral superior olive will have a ___ ______________ but will have ___ __________ if the sound is closer to the other ear
If the aural signal is closer to the ipsilateral ear, that lateral superior olive will have a net depolarisation but will have net inhibition if the sound is closer to the other ear
Each lateral superior olive gets a depolarising (from ___________ ear) and hyperpolarising (from _____________ ear) signal and each aural signal stimulates a lateral superior olive neurone from each _________
Each lateral superior olive gets a depolarising (from ipsilateral ear) and hyperpolarising (from contralateral ear) signal and each aural signal stimulates a lateral superior olive neurone from each hemisphere
The integration of excitatory and inhibitiory neurotransmission determines the ___ __________ that is forwarded to the _______ ________ and the lateral ________
The integration of excitatory and inhibitiory neurotransmission determines the net excitation that is forwarded to the inferior colliculus and the lateral lemniscus
What does the vestibular system provide information about?
- gravity
- rotation
- acceleration
What does the vestibular system serve as a reference for?
Somatosensory and visual systems
What does the vestibular system contribute to the integration of?
arousal, concious awareness of the body via connections with vestibular cortex, thalamus and reticular formation
What does the vestibular system allow for?
- gaze & postural stability
- sense of orientation
- detection of linear and angular acceleration
How does the vestibular organ know where you are going and which way is up?
By sensing;
- head angular acceleration (semicircular canals)- head rotation
- head linear acceleration (saccule and utricle)- translational motion, gravity (head tilt)
What is translational movement?
Linear movements in the x, y and z axes- primary concern of the otolith organs
What is rotational movement?
Body’s rotation relative to the x, y and z axes. the semicircular canals are primaroly responsible for sensing this.
What is the role of the peripheral sensory aparatus?
Vestibular organ
- detects and relays information to the vestibular nucleus about head angular & linear velocity to central processing system
- orients the head with respect to gravity
What is the role of the central processing system?
Processes information in conjunction with other sensory inputs for position and movement of head in space.
What is the role of the motor output system?
Generates compensatory eye movements and compensatory body movements during head and postural adjustments
What is the function of the semicircular canals?
Detect head movements via rotatory acceleration
Describe the structure of semicircular canals?
3 fluid-filled canals, right angles to each other, 1 for each major plane
Define crista
Sheet of cells where hair cells are clustered
Defind ampulla
bulge along canal containing crista
Where do cilia project to within the semicircular canals
Into gelatinous cupula
Kinocili are orientated in the ____ ______ so all are ______ or _______ together
Kinocili are orientated in the same direction so all are excited or inhibited together
What are semicircular canals filled with?
Endolymph
Movement causes fluid to _________ and displace _____
Movement causes fluid to circulate and displace cupula
Posterior canal shares plane with contralateral _______ canal.
Posterior canal shares plane with contralateral anterior canal.
What do the otolith organs sense?
Linear acceleration and gravity
What do the saccule and utricle detect?
Saccule : movement in the vertical/sagittal plane
Utricle: movement in the horizontal plane
Within the otolith organs hair cells lie in the ______, the ______ divides the hair cells into two populations with _______ ________.
Within the otolith organs hair cells lie in the macula, the striola divides the hair cells into two populations with opposing polarities.
Crystals of _______ ________ called _______ are on the _______ membrane
Crystals of calcium carbonate called otoconia are on the otolithic membrane
The striola arranges otoconia into narrow ______ dividing each _______
The striola arranges otoconia into narrow trenches dividing each otolith
Otoliths sense ______ acceleration of the head and change in _________ of the head relative to gravity.
Otoliths sense linear acceleration of the head and change in orientation of the head relative to gravity.
What other inputs are coordinated to the vestibular system?
Cortex, cerebellum, reticular formation, extra-pyramidal ststem
Vision
Proprioception, superficial sensation
Labyrinthine activity
What are the 3 major vestibular reflexes?
- vestibulo-ocular reflex- keep eyes still in space when the head moves
- vestibulo-colic reflex- keeps the head still in space or on a level plane when you talk
- vestibular-spinal reflex- adjusts posture for rapid changes in position
Describe the vestibulo-ocular reflex?
Designed to maintain clear and stable vision in the presence of head movements.
- causes eyes to move in the opposite direction to head movement
- speed of the eye movement equals that of the head movement
- allows objects to remain in focus during head movement
Which agents cause ototoxicity?
Aminoglycoside antibiotics and some chemotherapy agents
Why does vestibular system dysfunction occur when intoxicated?
alcohol is less dense than water, when you drink alcohol enters the blood, and then into the cupula. the cupula becomes less dense, it floats in the endolymph more. the cupula bends a little more than usual away from the ground. this bends hair cells, as if you are rotating even when you are still.
